This invention pertains to a chemical-mechanical polishing composition containing iodine and an iodine vapor-trapping agent.
Compositions and methods for planarizing or polishing the surface of a substrate are well known in the art. Polishing compositions (also known as polishing slurries) typically contain an abrasive material in an aqueous solution and are applied to a surface by contacting the surface with a polishing pad saturated with the polishing composition. Typical abrasive materials include silicon dioxide, cerium oxide, aluminum oxide, zirconium oxide, and tin oxide. U.S. Pat. No. 5,527,423, for example, describes a method for chemically-mechanically polishing a metal layer by contacting the surface with a polishing slurry comprising high purity fine metal oxide particles in an aqueous medium. The polishing slurry is typically used in conjunction with a polishing pad (e.g., polishing cloth or disk). Suitable polishing pads are described in U.S. Pat. Nos. 6,062,968, 6,117,000, and 6,126,532, which disclose the use of sintered polyurethane polishing pads having an open-celled porous network, and U.S. Pat. No. 5,489,233, which discloses the use of solid polishing pads having a surface texture or pattern. Alternatively, the abrasive material may be incorporated into the polishing pad. U.S. Pat. No. 5,958,794 discloses a fixed abrasive polishing pad.
Conventional polishing systems and polishing methods typically are not entirely satisfactory at planarizing substrates, especially memory disks. In particular, such polishing systems and polishing methods can result in less than desirable polishing rates and high surface defectivity when applied to memory or rigid disks. Because the performance of many substrates, such as memory disks, is directly associated with the planarity of its surface, it is crucial to use a polishing system and method that results in a high polishing efficiency, selectivity, uniformity, and removal rate and leaves a high quality polish with minimal surface defects.
There have been many attempts to improve the removal rate of memory or rigid disks during polishing, while minimizing defectivity of the polished surface during polishing. For example, U.S. Pat. No. 4,769,046 discloses a method for polishing a nickel-plated layer on a rigid disk using a composition comprising alumina abrasive and a polishing accelerator such as nickel nitrate, aluminum nitrate, or mixtures thereof. U.S. Pat. No. 6,015,506 discloses a method for polishing rigid disks using a polishing composition comprising a dispersion of a metal oxide abrasive, an oxidizing agent, and a catalyst having multiple oxidation states. WO 02/20214 discloses a method for polishing memory or rigid disk substrates using a polishing composition comprising an oxidized halide and an amino acid.
Polishing compositions often contain oxidizing agents, which can react with the surface of a substrate, particularly a metal-containing substrate like a memory or rigid disk, and render the surface more susceptible to removal by mechanical abrasion. Oxidizing agents containing iodine (e.g., iodine, iodides, iodates, and periodates) are particularly useful in polishing metal-containing substrates; however, their use can be accompanied by the generation and subsequent release of noxious iodine vapor into the atmosphere. In order to avoid this problem, additives that are capable of trapping the iodine vapor must be added to the polishing composition. For example, EP 1 118 647 A1 discloses the use of polymers and co-polymers comprising polyvinylpyridine and polyvinylpyrrolidone to trap iodine vapors during the polishing process. However, the inclusion of additives for trapping iodine can have a detrimental effect on the substrate removal rates during polishing. Thus, there remains a need for polishing compositions containing additives to control the formation of iodine vapor and allow iodine-based oxidizing agents to be used on an industrial scale. The invention provides such a composition. These and other advantages of the invention, as well as additional inventive features, will be apparent from the description of the invention provided herein.
The invention provides a chemical-mechanical polishing system comprising (a) an abrasive, a polishing pad, or both an abrasive and a polishing pad, (b) iodine, (c) an iodine vapor-trapping agent, and (d) a liquid carrier. The invention also provides a method of polishing a substrate using the chemical-mechanical polishing system.